Generally, a filtering dust collector captures dust particles from a gas by using a filtering cloth, and this dust collector is classified into various kinds in accordance with the method of removing the adhered dust particles. In a pulse jet filtering dust collector, a compressed air is periodically spouted into the inside of the filtering cloth in a direction opposite to the filtering direction, thereby detaching the adhered dust particles from the filtering cloth.
FIG. 1 is a perspective view of a part of the conventional filtering dust collector, and FIG. 2 is a sectional view of the conventional filtering dust collector. As shown in these drawings, a dust collecting tank 1 accommodates a plurality of filtering cloths 3 secured to a securing plate 2. A bag cage 4 is attached to each of the filtering cloths 3, and a venturi tube 5 is connected to the upper portion of the filtering cloth 3 within the filtering cloth 3.
Outside the dust collecting tank 1, there is installed a header cylinder 100 of an air header. This header cylinder 100 is provided with a plurality of discharge holes 101 on its top, and each of the discharge holes is connected to a ball valve 102. Each of the ball valves 102 is connected to a pulse valve 103, and each of the pulse valves 103 is connected to a connecting tube 106, while each of the connecting tubes 106 is connected to an air injecting pipe 13. Onto the wall of the dust collecting tank 1, the ends of the air injecting pipes 13 are secured by means of connectors 14. Each of the air injecting pipes 13 is provided with a plurality of nozzles 15, and each of the nozzles 15 is disposed directly above the opening of each of the filtering cloths 3. The other end of each of the air injecting pipes 13 is secured to the inside of the wall of the dust collecting tank 1 by means of a fastening member 16.
The pulse valve 103 has an inletting hole 103a in the lower portion of it and a discharge hole 103b in the front portion of it. The lower inletting hole 103a is connected to the ball valve 102, and the front discharge hole 103b is connected to the connecting tube 106, while a solenoid valve 104 is connected to a side of the pulse valve.
In this conventional filtering dust collector, the air which contains dust particles is introduced through an inlet 1a into the dust collecting tank 1, while the filtered air is discharged through an outlet 1b. In this manner, the dust particles which are contained in the air are filtered and adhered on the outside of the filtering cloth 3, with the result that the clean air is discharged through outlet 1b.
Periodically, the pulse valves 103 which are coupled to the header cylinder 100 are opened, and thus, the compressed air which is contained in the header cylinder 100 is spouted through the pulse valves 103 and through the nozzles 15 of the air injecting pipes 13 into the interior of the filtering cloths 3. Therefore, the filtering cloths 3 strongly vibrate, and the dust particles which adhere on the outside of the filtering cloths 3 are detached from the filtering cloths 3 to be collected to the bottom of the dust collecting tank 1. These collected dust particles are discharged from the bottom of the tank 1 through a rotary discharge valve 105.
In this conventional dust collector, the header cylinder is manufactured in the following manner. That is, flanges are welded to both ends of a cylindrical pipe, and compressed air supplying pipes are connected to the header cylinder. Further, the ball valves and the pulse valves are connected to the discharge holes of the header cylinder, and therefore, the constitution of the header cylinder is very complicated, while inconveniences are encountered when the plurality of the valves are assembled to the header cylinder. Further, there are other difficulties in maintaining the constant pitches and the constant straightness. In manufacturing the dust collector, the pipes have to be procured, drilled and welded, and therefore, the labor costs are increased, while the manufacturing period is extended.
Further, in the case where the pulse valves are directly connected to the header cylinder, and the solenoid valves are directly connected to the pulse valves, the pressure loss becomes seriously large during the actuation of the valves. Further, the pressure loss is voluminous at the bent portions of the pipes. Further, the inlets and the outlets of the valves are same with each other in their cross sections, and therefore, the flow amounts are small, as well as reducing the flow coefficient. Consequently, the dust detaching efficiency is aggravated.
Further, the pipes are corroded by the internal moisture of the header cylinder, and the resultant rusts are introduced into the valves to clog the bleed holes, thereby causing malfunctions in the valves.
Further, the solenoid valves and the timers are separately provided, and therefore, the assembling becomes very difficult, with the result that the manufacturing cost increases and the manufacturing period is extended.